The invention relates to an integrated amplifier arrangement, comprising a first and a second transistor, whose base electrodes lead to an input of the amplifier arrangement, whose emitter electrodes are coupled to each other, and whose collector electrodes lead to an output of the amplifier arrangement, which output is loaded by an output impedance, and via a load circuit to a supply terminal, the load circuit, in order to increase the gain at higher frequencies, comprising a third and a fourth transistor of the same conductivity type as the first and the second transistor, of which third and fourth transistor the respective main current path is connected in series with the main current path of the first and the second transistor, respectively, in that the emitter electrode of the third and the fourth transistor, respectively, is coupled to the collector electrode of the first and the second transistor, respectively, and the collector electrode of the third and the fourth transistor, respectively, is connected to said supply terminal via a first and a second impedance respectively, a third and a fourth impedance, being included in the base circuit of the third and the fourth transistor respectively.
Such an amplifier arrangement is known from an article by J. Choma in IEE Proceedings, Vol. 127, no. 2, April 1980, pages 61-66, entitled "Actively peaked broad-banded monolithic amplifier", in particular FIG. 7. In such an amplifier arrangement the inductive nature of the third and the fourth transistor, whose base circuits include the third and fourth impedance, is used to increase the gain and specific frequencies in order to compensate for the roll-off at higher frequencies owing to transistor characteristics and/or stray capacitances or even in order to peak the gain factor of the amplifier stage at specific frequencies. The base electrodes of said third and fourth transistors are then connected to a point of constant potential via said third and fourth impedances.
For various applications of high-frequency amplifiers, such as tuning circuit in, for example, television receivers, the amplifier should exhibit no low-frequency gain. As a result of d.c. and low-frequency gain any d.c. input voltages--caused by unequal settings of the first and the second transistor or by circuits preceding the first and the second transistor--appear amplified at the output, so that d.c. coupling to a following circuit with differential input is not readily possible. A solution for this is a capacitive coupling to the next circuit, but this has the drawback that the integrated circuit should be provided with additional terminals for the connection of the two capacitors required for this, that external components are necessary, that this results in high-frequency radiation and that the risk of instability thereby increases. Another possible solution is to eliminate the d.c. gain by means of low-frequency negative feedback via an at least partly external RC-network, which has similar drawbacks.
Due to these drawbacks it is difficult to combine sensitive high-frequency amplifiers on a single semiconductor substrate with other circuits such as frequency dividers, for example for television tuners.
Since several circuits are typically incorporated on a single semiconductor substrate it is moreover of importance to minimize the number of components and the power dissipation.